1. Technical Field
The disclosure relates to a liquid crystal display (LCD).
2. Description of Related Art
In general, thin film transistor (TFT) LCDs, for mobile phones, language translators, digital cameras, digital camcorders, personal digital assistants (PDAs), notebook computers, and desktop displays, can be categorized into transmissive TFT-LCDs, reflective TFT-LCDs, and transflective TFT-LCDs based on the way in which light sources are utilized and on the differences of array substrates. The transmissive TFT-LCD mainly adopts backlight as the light source. Pixel electrodes on a TFT array substrate of the transmissive TFT-LCD are transparent electrodes, so as to facilitate the penetration of light from the backlight source.
The reflective TFT-LCD mainly employs front-light or external light as the light source. The pixel electrodes on the TFT array substrate are metal electrodes or other reflective electrodes with good reflectivity suitable for reflecting the light from the front-light source or the external light source. On the other hand, the transflective TFT-LCD can be regarded as a structure that integrates both the transmissive TFT-LCD and the reflective TFT-LCD, and both the backlight source and the front-light source or the external light source can be utilized by the transflective TFT-LCD simultaneously to display images.
FIG. 1A is a partial cross-sectional view of a conventional transflective TFT-LCD panel. In a transflective TFT-LCD panel 100a having a single cell gap, a transparent pixel electrode 120a disposed in a transmissive region 104a and a metal pixel electrode 110a disposed in a reflective region 102a have identical heights.
Generally, in the transflective TFT-LCD panel 100a, the metal pixel electrode 110a in the reflective region 102a reflects the front-light source or the external light source, while the transparent pixel electrode 120a in the transmissive region 104a allows the light projected by a backlight module (not shown) to penetrate the transparent pixel electrode 120a. 
In detail, after the light from the front-light source or the external light source enters the TFT-LCD panel 100a, the light incident on the reflective region 102a is reflected by the metal pixel electrode 110a and then returns to the outside world from the TFT-LCD panel 100a. Moreover, the light provided by the backlight module penetrates the transparent pixel electrode 120a and the transmissive region 104a, and then passes through the TFT-LCD panel 100a to the outside world.
It should be noted that a distance that light beams travel through the reflective region 102a of a liquid crystal layer is approximately twice the distance that light beams travel through the transmissive region 104a of the liquid crystal layer. Therefore, the light beams transmitted through the reflective region 102a of the liquid crystal layer and those transmitted through the transmissive region 104a have different phase retardations. Under the circumstances, the transflective TFT LCD panel 100a has unfavorable display performance. When same voltages are respectively applied to liquid crystal molecules in the transmissive region 104a and in the reflective region 102a, the light beams should have a phase retardation of half the wavelength after passing through the transmissive region 104a, and should have a phase retardation of one quarter of the wavelength of light after passing through the reflective region 102a, so as to optimize opto-electrical properties.
FIG. 1B is a partial cross-sectional view of another conventional transflective TFT-LCD panel. As indicated in FIG. 1B, to resolve the above described issue, a method of fabricating a transflective TFT-LCD panel 100b having a dual cell gap has been developed.
Like TFT-LCD panel 100a, after the light from the front-light source or the external light source enters the TFT-LCD panel 100b, the light incident on a reflective region 102b is reflected by a metal pixel electrode 110b and then returns to the outside world from the TFT-LCD panel 100b. Moreover, the light provided by the backlight module penetrates a transparent pixel electrode 120b and a transmissive region 104b, and then passes through the TFT-LCD panel 100b to the outside world.
In the transflective TFT-LCD panel 100b having the dual cell gap, the cell gap of the transmissive region 104b is twice the cell gap of the reflective region 102b. Thus, in the reflective region 102b, a light path of the light entering from the front of the transflective TFT-LCD panel 100b is then equal to the light path of the light provided by the backlight module in the transmissive region 104b, so as to preclude the lights from having different light paths in the reflective region 102b and the transmissive region 104b. Therefore, the different opto-electrical performance in the two regions is avoided.
However, the dual cell gap raises complexity and difficulty in fabricating the TFT-LCD panel 100b. In light of the foregoing, manufacturing the transflective LCD penal having the single cell gap becomes an issue to be solved.